Preparation of long-chain esters of beta-thiodipropionic acid



Patented May 3, 1949' OFFICE PREPARATION OF LONG-CHAIN ESTERS OFBETA-THIODIPROPIONIC ACID William F. Gresham and Myers F. Gribbins, Wumington, Del., assignors to E. I. du Pont de Nemours & Company, porationof Delaware Wilmington, Del., a cor- No Drawing. Application April 8,1947, I Serial No. 740,268

Claims. (01. 250-481) This invention relates to a process for thepreparation of the higher molecular weight alcohol esters ofthiodicarboxylic acids and more particularly to the preparation of suchesters of thiodipropionic acid. 4

The 3-substituted mercaptoaliphatic organic acid esters and moreparticularly the mercaptopropionic acid esters have been found to beespecially effective anti-rancidity agents for use in oils, fats, waxesand the like, as is described in the D. K. OLeary and in the Gribbins etal. Patents 2,397,960 and 2,397,976 of April 9, 1946. These esters havelikewise been found suitable for use in soap for preventing rancidity asis described in the Gribbins Patent 2,416,052 of February 18, 1947.These uses demand esters of high quality that are not only colorless,for off-color is highly undesirable in soaps, food products and thelike, but also odorless, for foreign odors are not tolerated in foods orin the better grades of soap and soap products.

An object of the present inventionis to provide a process for thepreparation of esters of 3- substituted mercaptolaliphatic organic, acidesters which are substantially colorless and odorless. A further objectis to provide a process for preparing the higher aliphatic alcoholesters of these 3-substituted mercaptopropionic acids and moreparticularly such esters of 3-substituted mercaptopropionic acid by thealcoholysis of the lower alkyl esters of 3-substituted merpaptopropionicacid, more particularly the methyl ester with higher aliphatic alcohols.Other objects and advantages of the invention will hereinafter appear.

The invention is directed to the preparation of substantially colorlessand odorless higher aliphatic alcohol esters of a beta-thioether of anester of propionic acid having the formula:

ROOCCHzCHzS-X group and more particularly, thosecontaining from 10 to 24carbon atoms and in which X is:

' 1. A hydrocarbon group such as e. g.: the alkyl groups: methyl, ethyl,propyl, butyl, lauryl, and the aryl groups: phenyl, naphthyl, benzyl;and such groups as cyclohexyl; v

2. An oxygenated-hydrocarbon group such as e. g.: the alcohol groups:hydroxymethyl, hydroxyethyl, and hydroxybutyl; the ether-groups;

2 methoxymethyl, methoxyethyl, and ethoxyethyl; the acid groups and theR esters thereof: carbonymethyl, carboiwethyl, carbo'xypropyl andcarboxybutyl; and the aldehyde groups such as aldehydroethyl;

3. A sulfur-hydrocarbon group such as e. g.: mercaptoethyl,mercaptopropyl, mercaptobutyl, mercaptoisobutyl, mercaptohexyl andethiaethyl.

4. A sulfurand oxygenated-hydrocarbon group such as e. g.:carboxyethiaethyl,

-CH2CH2SCH2CH:COOH carboxyethiaethdithiaethyl,

-cH2cHsscH2cH2scH2cH=coon carboxythiaisobutyl,

-CH 2CH2CH(CH3) SCHzCHzCOOH and carboxyethiapropyl,

is maintained until substantially no more of the lower alcohol, which isformed by the interchange, distills over, the product is then cooledrapidly to 40 to 50 C. and a suflicient amount of water and caustic sodaor alkali dissolved in water added to neutralize the acid catalyst used.l Neutralization is carried out as accurately as possible in order notto contaminate the product. After filtering off the precipitatedcatalyst (a catalyst and neutralizer being selected such that a.precipitate is obtained, such for example, as sulfuric acid and bariumhydroxide or phosphoric acid and sodium hydroxide) the filtered ester issubjected to a deodorizing treatment by passing it countercurrent to theflow of steam at a temperature between. and 225 C. and under a vacuum ofless than about 40 millimeters, preferably below 20 millimeters.

The example which follows illustrates a preferred embodiment of theinvention in which parts are by weight unless otherwise indicated.

Eq:ample.-Stoichiometric amounts of dimethyi thiodipropionate and amixture of alcohols, prinabsolute'to facilitate cipally l'auryl alcoholobtained in water was added (1% acid based on the ester) sac 99.2... I

by the cartons-' and the-temperature raised as rapidly-as possible to2009p mately two hours.

-150-l60 C. .(made evident by the evolution of where it was'main'tainedior' approxi- The reaction started at niethanol) andproceeded quiterapidly until about I about 7 5 wasred'uced to about.290;millinije1ters'of mercury pl'ete methanol removaL- when thereaction-{was}.completed ino more distiliate coming oif) the-product wascooled rapidly I to 4,0 to 50 C. and the proper amounts 0! watercormilete.v At this 'point'th 'pre s and sodium hydroxidedissolvedinwater added to neutralize 'the phosphoric acid catalyst toNaaHPOe'IHzC). The product was then"cooled to room temperature andfiltered.

The above product was. further- 7 subjecting it to acountercurrent steamscrubbing proximately 190 C. (although temperatures be- 1'iormed,?.t Itemperature .2. The process of clalm'l in which the product isdeodorized by subjecting it to countercurrent v scrubbingwith steam, thescrubbing operation being'conducted at a temperature between 150 C,- to.225": C. and at absolute.

A' process for thepreparation of a substantially odorless: and tastelessstearylalcohol ester g, p e ure below 100 mm. B!

Lot betaathiodipropionic-acid, which comprises hea ing ethy betathiodipi'opionate with stem] alcohol-inthe presenceloi anxacid catalystwhile withdrawingthe methanolas formed, the reaction being conducted ata temperature below process .t or the "preparation or a substana ,tiallyodorless and tasteless higher. alcohol ester deodorized by":

operation maintained at a. temperature of apliquid stream of the-esterwas continuously passed into-the top of areaction vessel andcontinuously withdrawn from'the bottom, superheated steam passingthrough the vessel counter-current to the now of ester, thedeodorization being conducted at apressure'below 100 mm. and preferablyas in this example, between. and mm; Hg absolute pressure. The productobtained in accord with this process was substantially odorless andcolorless and wholly acceptable for comestible The other higheraliphatic alcohol esters of the other 3-substituted dicarboxylic acidsmay similarly prepared to give products thatare both odorless andtasteless" by reacting these-alcohols withthe methylfesters of the acidsand subsequently it necessary removing the final traces-of odor'by thecountercurrent flow steam distiila- Y vtiorrprocess. v I.

"We claim:

' '1. Av process for the preparation of a substantially odorless andtasteless monohydric alcohol-,

.- of beta-thiodipropionlc acid, the higher alcohol consisting ofamixture or higher alcohols, pre "dominately lauryl alcohol, obtained bythe catalytic hydrogenation of fats and oils underelevatv edtemperaturesl a'nd pressures, which comprises tween and 300.(3..maybeiusedl wherein-a.

heating" methyl beta-thlodipropionate with the aforesaid-higheralcohol-in the presence of an acid catalyst while withdrawing themethanol as formed, the reaction being conducted at a temperature below250C; '5.2.A- process tor thepreparation of a substan tially odorlessand tasteless monohydric alcohol ester of .beta-thiodipropionic acid,the alcohol containing 10in 24 carbon atoms, which. comprises heatinga'lower dialkyl ester of beta-thicdipropionic, acid with amonohydricalcohol containing 10 to 24 carbon atoms in the presence of an acidcatalyst while withdrawing the lower boiling alcohol formed, thereaction being conducted at a temperature below 250C.

WILLIAMEGRESHAM.

MYERS F; GRIBBINS.

REFERENCES CITED The'following references are of record in the file ofthis patent:

. UNITED STATES PATENTS Number in thepresenoeoi -e d-Qata shflewlthdrawing themethan'ol' conducted at a p Certificate of CorrectionPatent No. 2,468,725.

. May 3, 1949.

WILLIAM F. GRESHAM ET AL.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring correction as follows:

Column 2, lines 4 and 5, for the Word aldehydroethyl read aldehydoethyl;line 16, for carboxythiaisobutyl read carbozyethiaisobutyl;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 11th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

